The invention relates to a propulsion control system for motor vehicles for maintaining stable driving conditions.
This type of system, shown in DE-PS No. 19 02 944, is a control device for avoiding swerving in turns in the case of motor vehicles. A plurality of measured and calculated quantities are obtained from a gyroscope and several sensors, and provided, in a way that is not shown, control signals for the brake system as well as a power control element of the internal-combustion engine. In this case, three programs for different road conditions are provided that have to be selected by the driver.
This type of system is not satisfactory with respect to manufacturing technology because it is much too costly, nor with respect to the application. It can be anticipated what would happen should the driver forget to select the program assigned to the actual road conditions.
For stabilizing a vehicle that enters the limiting range with respect to driving dynamics, the shifting from a single-axle to a multi-axle drive is known. Wheel slip control systems (ASR) and antilocking brake systems (ABS) are also known. However, all these systems cannot keep a vehicle in all cases from exceeding the limits of driving dynamics.
It is the objective of the invention to achieve this goal in a better way and with means that are simpler than the known means and to provide a system that can keep a vehicle from exceeding stable road conditions and from being damaged or destroyed as a result.
For rear wheel drive vehicles, the speed difference of the front wheels is compared to the tolerance range. According to the invention, this objective can be achieved by the following. From the measured quantities of steering angle and driving speed, a value or a tolerance range around the value of the speed difference of the front wheels or of the lateral acceleration or of the yaw velocity is calculated according to known formulas and is compared with the measured value of these quantities. The result of the comparison, i.e., the amount by which the measured value exceeds the calculated value or is outside the tolerance range, is the measurement for the intervention into the braking system or the power control element of the internal-combustion engine.
For rear wheel drive vehicles, the speed difference of the front wheel is compared to the tolerance range. For vehicles with all-wheel drive, if a wheel slip control system is operative at the same time, the difference of the front wheel speeds supplies no practically usable signals. However, this type of vehicle concept can be stabilized by using instead the lateral acceleration or the yaw velocity.
The advantage of the system according to the invention, in comparison to the known system, is that by means of a few, easily obtainable input quantities, a control of the vehicle can be achieved with respect to driving stability.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.